1. Field of the Invention
The present invention relates to an electric heating device for a motor vehicle, comprising at least one PTC heating element with contact metal sheets extending substantially parallel to one another and accommodating between them at least one PTC element, and a printed circuit board having formed therein at least one opening through which a contact tongue projects, which is defined by a contact metal sheet and which serves to establish an electric connection between the PTC heating element and the printed circuit board.
2. Description of the Related Art
Such electric heating devices, which are also referred to as PTC heating devices, are used in motor vehicles for the purpose of heating. EP 1 157 867, for example, discloses an electric heating device in which a plurality of heat-generating elements are accommodated in a frame, said heat-generating elements being defined by two contact metal sheets extending parallel to one another and by PTC elements successively arranged between said contact metal sheets in one plane. These heat-generating elements are provided in alternating sequence with heat-emitting elements. The thus defined layered structure is held in a pretensioned manner in a frame.
Selected ones of these contact metal sheets of the individual heat-generating elements are laterally extended beyond the heating block so as to provide contact tongues for electrically connecting thereto the heating block. In EP 1 157 867 these contact tongues extend through openings in a printed circuit board populated with components. On the side facing away from the heating block, the printed circuit board carries a spring element which projects beyond the printed circuit board, said spring element clamping the contact lug and effecting electric contacting with the printed circuit board.
A similar structural design with respect to contacting between the contact tongue and the printed circuit board is known from EP 1 872 986. In the case of this prior art, two respective contact metal sheets accommodate between them a plurality of PTC elements that are stacked one on top of the other. The resultant heat-generating element is pretensioned by a wedge element acting from outside, said wedge element resting on a pocket and being forced into said pocket, so that the individual layers abut on one another in good contact with one another. Hence, the wedge element has the function of a spring by means of which the layered structure is held in a pretensioned manner within the frame in the case of EP 1 157 867 A1. Also in EP 1 872 986 the contact tongues defined by the contact metal sheets extend through openings in the printed circuit board so as to be clamped in position in spring elements projecting beyond the printed circuit board on the back facing away from the heat-generating elements.